Mechanical ventilation is a method to mechanically assist or replace natural breathing in a subject.
Mechanical airway ventilation (MV) of a subject/patient can be subdivided into two major categories: invasive (IV) and non-invasive ventilation (NW). Invasive ventilation uses an endrotracheal tube or tracheotomy to restore alveolar ventilation and gas exchange. NW is used to provide patients with respiratory support through a mask without the invasive nature of an intubation or tracheotomy (Kinnear W J M. Non-Invasive Ventilation Made Simple. Nottingham University Press, 2007). Ventilation entails a range of medical ventilator support techniques such as, but not limited to Continuous Positive Airway Pressure (CPAP), Non-invasive Positive Pressure Ventilation (NIPPV), Bi-Level Positive Airway Pressure (BiPAP), Intrapulmonary percussive ventilation (IPV), and Mechanical Insufflator-Exsufflator.
IPV and Mechanical Insufflator-Exsufflator techniques are mainly used in physiotherapy to improve the patient's breathing through the removal of excessive mucus.
IV is usually applied to patients that cannot breathe independently, typically in an intensive care unit. The respirator provides respiratory flow often without the requirement for patient effort. Pressure and volume controlled modi can be used and the patient can in some settings still trigger the ventilator. NIV on the other hand can offer the same support (also completely volume controlled or pressured controlled with or without back-up volume) but mostly patients still trigger the ventilator. NIV is often used in patients with restrictive neuromuscular diseases such as amyotrophic lateral sclerosis (ALS), myotonic dystrophy (Steinert's disease), Duchenne muscular dystrophy, Acid maltase deficiency, and Emery-Dreifuss myopathy.
Recently, NIV has been used increasingly in chronic obstructive pulmonary disease (COPD) patients. Recent studies indicate that NIV in COPD can have a beneficial effect although the data are not always conclusive (Dreher M, Kenn K and Windisch W. Non-invasive ventilation and physical exercise in patients with COPD. Pneumologie 62: 162-168, 2008; McEvoy R D, Pierce R J, Hillman D, Esterman A, Ellis E E, Catcheside P G, O'Donoghue F J, Barnes D J and Grunstein R R. Nocturnal Non-Invasive Nasal Ventilation in Stable Hypercapnic COPD: A Randomised Controlled Trial. Thorax 2009; Windisch W, Haenel M, Storre J H and Dreher M. High-intensity non-invasive positive pressure ventilation for stable hypercapnic COPD. Int J Med Sci 6: 72-76, 2009). It is the general impression that a subset of the patient population may benefit significantly from NIV, while the effect is less pronounced in other patients.
With a mechanical ventilator, several parameters must be adjusted according to the patient needs, including, for instance, pressure, volume of gas, respiratory rate, rise time, I:E ratio, trigger mode and sensitivity. The correct parameters are necessary to restore alveolar ventilation, prevent atelectasis, and optimize gas exchange. Moreover, MV carries many potential complications including pneumothorax, airway injury, alveolar damage, and ventilator-associated pneumonia. For this reason the settings of the MV must be carefully determined. Typically the adjustments of the ventilator settings are still empirical, using the obtained gas exchange reflected in blood gas analysis, oxygen saturation and CO2 monitoring as guidance.
The aim of the present invention is to optimize the setting of the parameters for MV, which allows more subsets of the population to benefit, and also to reduce treatment failures due to an excessively long or inadequate start up period.